As conventional methods for crystallization of amino acid, there have been proposed a method for crystallization which comprises concentrating an aqueous solution of amino acid under reduced pressure, a method which comprises neutralization for crystallization, a method which comprises crystallization with a solvent while adding a lower alcohol or a ketone to the aqueous solution in large quantities, and so on (cf. Japanese Patent Application Laid-Open Nos. 59-39857, 59-45898, etc.).
Among these methods, in the method for crystallization which comprises concentration under reduced pressure, fine amino acid crystals precipitated tend to take bubbles in the crystals and cause bumping so that care must be required for the concentrating operation. Furthermore, according to the method which comprises neutralization for crystallization, crystals tend to float on the upper layer of the solution and the crystals do not grow as expected and in most cases, therefore, it might take time for solid-liquid separation. On the other hand, the method which comprises crystallization of amino acid by adding a lower alcohol or a ketone requires separate equipments for recovering the organic solvent, which not only leads to complicated process but is also economically disadvantageous, because it is impossible to completely recover the solvent.
Accordingly, it is significant in the art to provide a method for crystallization of amino acid having a high purity, in a simple manner using simple apparatuses.